#include <bits/stdc++.h>

int main() {
  std::cin.tie(nullptr)->sync_with_stdio(false);
  int T;
  std::cin >> T;
  while (T--) {
    int N;
    std::cin >> N;
    std::vector<int> A(N);
    for (int& e : A) { std::cin >> e; }
    std::sort(A.begin(), A.end());

    bool even = ~N & 1;
    if (even) {
      ++N;
      A.push_back(int(1e9));
    }

    std::adjacent_difference(A.begin(), A.end(), A.begin());

    int ans = A[0];
    std::priority_queue<int> q;
    for (int i = 1; i < N; i += 2) {
      q.push(A[i]);
      q.push(A[i + 1]);
      ans += q.top();
      q.pop();
    }

    if (even) { ans = int(1e9) - ans; }
    std::cout << ans << '\n';
  }
}